Overall Summary The prevalence of dementia increases with advancing age. However, some cognitive decline is expected to occur as part of normal aging beginning in early adulthood. Differentiating normal from pathological cognitive change across the adult lifespan along with associated risk factors is essential for both preventing and treating abnormal cognitive decline. Unfortunately, current ability to do this is hampered by a lack of sensitive assessment tools that can be easily and widely deployed in diverse research designs and populations. We will address this limitation by developing, validating, norming, and disseminating a MobileToolbox of cognitive assessments appropriate for remote smartphone administration in adults aged 20 to 85. We will accomplish this objective via the following aims: 1. Create the MobileToolbox Library of iOS and Android smart-phone based assessments. These will draw from our existing work within NIH Toolbox, International Cognitive Ability Resource (ICAR), ResearchKit, ResearchStack, and the FaceName Test. The MobileToolbox will also enable delivery of additional measures of variables (e.g., mood) known to be important co-variates of cognition including measures from the Patient Reported Outcomes Measurement Information System (PROMIS) and other measurement collections. The library will be open source and available for integration of additional externally developed tests. 2. Develop and maintain the MobileToolbox Research Platform, a software platform to support clinical researchers and software developers in the dynamic, customizable integration of Mobile Toolbox Library into research studies. This will be developed as an extension of the platform built by Sage Bionetworks to support the 2015 launch of Apple?s ResearchKit. The Platform will support researchers to contribute or select assessments, to manage study and assessment protocols, and to receive, store, aggregate, analyze and share (as appropriate) data collected using iOS and/or Android smartphone devices. 3. Conduct psychometric activities to validate, norm and assess the reliability of the MobileToolbox in both general population and various research samples to create general population reference norms. The cognitive assessments will be validated against gold standard measures in healthy adults ages 20-85. The measures will then be normed and 3-month, 12-month and 24-month change scores calculated in an age- stratified (20-85), iOS vs Android, national sample matching the 2020 US Census (N=6,800) for gender, race, ethnicity, SES and level of education. Additional validation and longitudinal evaluation will be conducted in healthy and clinical samples, including persons at risk for MCI or AD, cognitively impaired and those with Parkinson?s disease.